Plasticity Modeling of Concrete Confined With NiTiNb Shape Memory Alloy Spirals

Concrete confinement is proved to be an effective method to improve concrete strength and ductility. In recent years, a novel confinement technique using NiTiNb shape memory alloy (SMA) spirals was proposed and proved to be promising for seismic retrofit of concrete structures. Despite the experimental work that has been done in this area, there is few computational tools available that are capable of describing the three-dimensional constitutive behavior of NiTiNb-SMA confined concrete. This paper proposes a plasticity-based NiTiNb-SMA confined concrete constitutive model, which is capable of predicting and simulating three-dimensional stress-strain behavior of NiTiNb-SMA confined concrete under both monotonic and cyclic loading. New hardening/softening function, dilation rate function and damage parameter are derived and validated based on experimental results. The proposed model is able to closely simulate the axial and lateral stress-strain behaviors of NiTiNb-SMA confined concrete when compared to experimental results.